The invention relates to battery jumper cables and particularly to those comprising a first electrically insulated flexible low-voltage conductor having each end portion electrically connected to a pair of electrically insulated pole pliers, and a second electrically insulated flexible low-voltage conductor having each end portion electrically connected to a pair of electrically insulated pole pliers.
Known conventional battery jumper cables (see for instance DIN 72,553 in the draft version of February 1987) are intended for use with a first vehicle having internal combustion engines for temporarily transmitting electrical power required for starting from a storage battery of a second vehicle.
German patent specification Nos. 2,718,188 and 3,228,471 disclose surge arresters for diverting lightning stroke currents, comprising a varistor and a surge arrester which is electrically connected in parallel therewith and having a lightning stroke current-carrying air spark gap. Further, German Laid-open Publication 2,920,979 discloses a surge arrester for protecting low-voltage switchgear, including a metal oxide varistor and a surge arrester connected in parallel therewith and having an air spark gap. However, such surge arresters have not been used so far in conjunction with battery jumper cables.
For many years motor vehicles have included electronic systems and components, for instance in ignition electronics and in fuel injection systems. Anti-skid and anti-slip systems developed recently also comprise a considerable number of electronic components.
It has been found that considerable reactive peak voltages may occur when conventional battery jumper cables are used. Especially when the storage battery of the second vehicle is the starting battery and the engine of the second vehicle is running when the pairs of pole pliers are removed from the battery terminals after the jumping operation has been successful, high peak voltages may occur which are accompanied by considerable spark formation. Within a range of micro- or milli-seconds, voltages in excess of 1000 V may occur, which present a grave risk to expensive electronic parts and components of modern vehicles.